GRIB/JPEG2000 Scaling Differences

[warmerdam]

Examining channel 7 of gfs06zf03.grib2 we see the scaling of the values differs significantly depending on whether they are read with JP2KAK or JP2ECW.

JP2KAK

Band 7 Block=360x1 Type=Float64, ColorInterp=Undefined
  Description = 2000[Pa] ISBL="Isobaric surface"
    Computed Min/Max=24099.689,24279.850

JP2ECW

Band 7 Block=360x1 Type=Float64, ColorInterp=Undefined
  Description = 2000[Pa] ISBL="Isobaric surface"
    Computed Min/Max=24099.689,26901.289

I think this is more an issue with how the different jpeg2000 drivers handle non-integer datasets than it is about the grib driver itself.

JasPer looks like:

Band 7 Block=360x1 Type=Float64, ColorInterp=Undefined
  Description = 2000[Pa] ISBL="Isobaric surface"
    Computed Min/Max=24099.689,26901.289

Based on this, and visual examination, I am now supposing this is a problem with the JP2KAK driver. I will extract the jpeg2000 data stream for this band and dig into it deeper.

[warmerdam]

I see that the JP2KAK driver now produces the same values as the other drivers so apparently the issue was solved in either Kakadu itself or the JP2KAK driver in the meantime.